Method and apparatus for drawing sheet metal



Oct. 18, 1-949. 1 v J. B. BRENNAN 2,485,354

- METHOD AND APPARATUS FOR DRAWING SHEET METAL Filed May 10, 1945 2 Sheets-Sheet l INVENTOR. JOSEPH B.BRENNAN ATTOR NEYS Oct. 18, 1949. Y J. B; BRENNAN 2,485,354

METHOD AND APPARATUS FOR DRAWING SHEET METAL Filad May 10, 1945 v 2 Sheets-Sheet 2 ,19. INVENTOR. v JOSEPH B.BRENNAN M CQWAAJJ.

ATTORNEYS Patented Oct. 18, 1949 UNITED STATES PATENT OFFICE METHOD AND APPARATUS FOR DRAWING SHEET METAL J oseph B. Brennan, Bratenahl, Ohio Application May 10, 1945, Serial No. 593,009

art to provide rather expensive complementary dies which are then placed in a press and the sheet metal blank deformed by means of the coacting dies which operate under high pressure. Such procedure necessitates dies of particular materials and cut to close tolerances and a press for actuating the same which is quite expensive because of the pressures required to be developed.

It is an object of the present invention to provide an apparatus for and mode of working sheet metal by which deep draws may be made by apparatus which is relatively inexpensive and which can utilize many grades of common steel which cannot be deep drawn in presses of the character previously described which generally require special alloys.

Other objects of the invention will appear as the description proceeds.

To the accomplishment of the foregoing and related ends, said invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawings:

Fig. 1 is a perspective view of an apparatus constructed in accordance with the principles of my invention;

Fig. 2 is a perspective view of a sheet metal part formed by the particular apparatus illustrated in Fig. 1;

Fig. 3 is a transverse sectional view on a vertical plane through the apparatus of Fig. 1; and

Fig. 4 is a view similar to Fig. 3 but showing a further modification of my invention.

Referring now more specifically to the drawings and more especially to Figs. 1 and 3, the apparatus here illustrated comprises a conventional drop hammer which includes a base indicated at l and a head 2. Drop hammers of the character to which my invention relates are wellknown in the art and usually consist of a hammer 2 carrying a punch 3 which is adapted to operate on the work supported by a pillowblock or die 4. The intensity of the blow delivered by the hammer, or more specifically the punch attached to the hammer, is determined by the height to which the hammer is raised before it is then permitted to drop by gravity to deliver a blow to the work. As previously indicated, such construction is conventional in the art and the apparatus in those particulars will not be more fully illustrated o'r described.

My invention is concerned with the provision of a draw or clamping ring 5 which is arranged over the die 4 and elevated and lowered with respect to such die by means of a plurality of fluid actuated jacks 6 of which four are illustrated .in Fig. 1, although any desired number may be employed.

The jacks 6 are conventional, twp-way rams preferably actuated hydraulically by means of fluid introduced to the opposite ends thereof through conduits and 8. The conduits I and Bare in communication with main conduits 9 and m respectively which are adapted to be connected to pressure and drain conduits H and I2 by means of a four-way valve 13.

The draw or clamping ring 5 is provided with an opening I4 therein closely conforming to the cross-sectional configuration of the punch 3.

In the operation of the apparatus just described, a blank of usually flat sheet steel is placed over the die 4, and then the clamping or draw ring 5 lowered into engagement therewith and clamped by means of the jacks 6. The hammer is then actuated to deliver a succession of blows to the blank 15 progressively forcing the same into the matrix of the die 4 until the blank conform to the configuration of such ma-. trix. Generally after this is accomplished, the hammer will be caused to strike the formed blank sharply and with substantial force to set the same so that there will be no spring-back or recovery of the metal comprising the formed part.

I6 such as is illustrated in Fig. 2.

From the foregoing description it will be observed that the apparatus comprising my invention may be utilized for the purpose of applying a variable amount of pressure onto the clamping ring which engages the blank being operated upon around the entire periphery of the area of the blank which is engaged by the punch 3. Thus, the clamping pressure may be accurately controlled so as to compensate for variations in thicknesses, ductility, etc. of the blank being operated upon. By making the valve I 3 manually operable, the operator performing the drawing operation is able to inspect the state of the work piece during successive hammer blows and if any evidences of uneven drawing, i. e. thinning or the pressure line I 1 leading to the jacks 6 has included therein a pressure regulating valve diagrammatically illustrated at l8. Connected .in parallel in the line H with the pressure regulating valve i8 is a manually operable pressure regulating valve l9.

The actuating handle 20 of the regulating valve I8 is connected by means of a rod 2| to a bracket 22 carried by the hammer of the press. The rod 2| extends through an opening in the bracket 22 and has a collar 23 adjustably secured thereto whereby the rod 2| will be caused to move upwardly to a position corresponding with the uppermost position of the hammer 2.

In order to hold the rod 2| in an elevated position during successive hammer blows, it is arranged to pass through an opening in a bracket 24 which carries a frictional detent 25 engaging the rod 2! and holding it in an elevated position as the hammer 2 drops.

The apparatus illustrated in Fig. 4, therefore, provides a convenient means for progressively varying the pressureapplied by means of the jacks 6 to the clamping or draw ring as the intensity of the blows delivered by the hammer 2 varies due to variations in the height to which the hammer is raised.

For certain types of metal, the clamping pressure should be progressively increased as the intensity of the hammer blows is increased, and when working on other types of metal, the clamping pressure should vary inversely with the intensity of the hammer blows. This can be accomplished by appropriate setting of the pressure regulating valve 18 and appropriate connection thereto by means of the rod 2|.

In order to make it possible for the operator to independently vary the clamping pressure, I provide the shunt valve [9 which is manually operable and by which the operator can adjust the clamping pressure as occasion may require in view of his inspection of the work piece during the actual forming operation in the manner previously explained.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

I, therefore, particularly point out and distinctly claim as my invention:

1. The method of drawing sheet metal which comprises placing a blank of sheet metal over a die, clamp-ing such blank to said die, deforming the blank into said die by means of successive hammer blows of varying intensity, and varying said clamping pressure progressively during said drawing operation in accordance with variations in the force of the blows but independently of the resistance to drawing offered by such blank and solely in the interim between successive hammer blows.

2. Apparatus for forming sheet metal, comprising a pair of dies movable throughout varying distances toward and away from one another, a clamping member between said dies adapted to clamp a work piece blank against one of them, fluid pressure means for actuating said clamping member, means for regulating said fluid pressure having an adjustable element, means connecting said element to the other of said dies to vary the clamping pressure solely in accordance with the amount of separating movement of said dies, and means for holding said element at the position to which it was actuated upon subsequent movement of the dies toward one another.

3. Apparatus for forming sheet metal, comprising a pair of dies movable throughout varying distances toward and away from one another, a clamping member between said dies adapted to clamp a work piece blank against one of them, fluid pressure means for actuating said clamping member, a valve for regulating said fluid pressure having an adjustable element, means connecting said element to the other of said dies to Vary the clamping pressure solely in accordance with the amount of separating movement of said-dies, and means for holding said element at the position to which it was actuated upon subsequent movement of the dies toward one another.

4. Apparatus for forming sheet metal, comprising a vertically reciprocable drop hammer movable throughout varying distances, a die axially therebelow, a clamping member for peripherally clamping a sheet metal blank to said die, fluid pressure means for actuating said clamping member, means for regulating said fluid pressure having an adjustable element, means connecting said element to said hammer to vary the clamping pressure solely in accordance with the position to which said hammer is raised, and means for holding said element at the position to which it was actuated upon subsequent movement of the hammer toward said die.

5. Apparatus for forming sheet metal, comprising a vertically reciprocable drop hammer movable throughout varying distances, a die axially therebelow, a clamping member for peripherally clamping a sheet metal blank to said die, fluid pressure means for actuating said clamping member, a valve for regulating said fluid pressure having an adjustable element, means connecting said element to said hammer to vary the clamping pressure solely in accordance with the position to which said hammer is raised, and means for holding said element at the position to which it was actuated upon subsequent movement of the hammer toward said die.

JOSEPH B. BRENNAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 504,878 I-Ieslop Sept. 12, 1893 674,647 Drennan May 21, 1901 814,568 Stagg Mar. 6, 1906 1,503,131 Nelson July 29, 1924 2,070,720 Ernst Feb. 16, 1937 2,075,847 Hothersall Apr. 6, 1937 2,143,429 Auble Jan. 10, 1939 2,192,778 Stacy Mar. 5, 1940 2,419,563 Kaser Apr. 29, 1947 I FOREIGN PATENTS Number Country Date 6,686 Great Britain Apr. 22, 1884 12,110 Great Britain May 27, 1898 

